diff options
| author | Tom Rondeau | 2011-09-26 23:23:14 -0400 |
|---|---|---|
| committer | Tom Rondeau | 2011-09-26 23:23:14 -0400 |
| commit | 4fec8eba2eb3d362319c8e09bf370edaa10cd1b9 (patch) | |
| tree | e41ff025b20b5c4ad8928fa0651a06dca884dc6f /gr-vocoder/lib/codec2/pack.c | |
| parent | 79e7183bda0e3850c79dee7f086a8676311607fa (diff) | |
| parent | e3b56bfd879f16c2fa1f284f330ed3df6a211ec1 (diff) | |
| download | gnuradio-4fec8eba2eb3d362319c8e09bf370edaa10cd1b9.tar.gz gnuradio-4fec8eba2eb3d362319c8e09bf370edaa10cd1b9.tar.bz2 gnuradio-4fec8eba2eb3d362319c8e09bf370edaa10cd1b9.zip | |
Merge branch 'next' into digital
Conflicts:
gnuradio-core/src/lib/general/general.i
gnuradio-core/src/lib/general/gr_pll_carriertracking_cc.cc
gnuradio-core/src/lib/general/gr_pll_freqdet_cf.cc
gnuradio-core/src/lib/general/gr_pll_refout_cc.cc
gnuradio-core/src/python/gnuradio/gr/qa_pll_carriertracking.py
gnuradio-core/src/python/gnuradio/gr/qa_pll_freqdet.py
gnuradio-core/src/python/gnuradio/gr/qa_pll_refout.py
gr-digital/lib/digital_constellation_receiver_cb.cc
gr-digital/python/Makefile.am
gr-digital/python/__init__.py
gr-digital/python/generic_mod_demod.py
gr-digital/python/pkt.py
gr-digital/python/psk2.py
gr-digital/python/qam.py
Diffstat (limited to 'gr-vocoder/lib/codec2/pack.c')
| -rw-r--r-- | gr-vocoder/lib/codec2/pack.c | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/gr-vocoder/lib/codec2/pack.c b/gr-vocoder/lib/codec2/pack.c new file mode 100644 index 000000000..31551dfc4 --- /dev/null +++ b/gr-vocoder/lib/codec2/pack.c @@ -0,0 +1,105 @@ +/* + Copyright (C) 2010 Perens LLC <bruce@perens.com> + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. + + */ +#include "defines.h" +#include "quantise.h" +#include <stdio.h> + +/* Compile-time constants */ +/* Size of unsigned char in bits. Assumes 8 bits-per-char. */ +static const unsigned int WordSize = 8; + +/* Mask to pick the bit component out of bitIndex. */ +static const unsigned int IndexMask = 0x7; + +/* Used to pick the word component out of bitIndex. */ +static const unsigned int ShiftRight = 3; + +/** Pack a bit field into a bit string, encoding the field in Gray code. + * + * The output is an array of unsigned char data. The fields are efficiently + * packed into the bit string. The Gray coding is a naive attempt to reduce + * the effect of single-bit errors, we expect to do a better job as the + * codec develops. + * + * This code would be simpler if it just set one bit at a time in the string, + * but would hit the same cache line more often. I'm not sure the complexity + * gains us anything here. + * + * Although field is currently of int type rather than unsigned for + * compatibility with the rest of the code, indices are always expected to + * be >= 0. + */ +void +pack( + unsigned char * bitArray, /* The output bit string. */ + unsigned int * bitIndex, /* Index into the string in BITS, not bytes.*/ + int field, /* The bit field to be packed. */ + unsigned int fieldWidth/* Width of the field in BITS, not bytes. */ + ) +{ + /* Convert the field to Gray code */ + field = (field >> 1) ^ field; + + do { + unsigned int bI = *bitIndex; + unsigned int bitsLeft = WordSize - (bI & IndexMask); + unsigned int sliceWidth = + bitsLeft < fieldWidth ? bitsLeft : fieldWidth; + unsigned int wordIndex = bI >> ShiftRight; + + bitArray[wordIndex] |= + ((unsigned char)((field >> (fieldWidth - sliceWidth)) + << (bitsLeft - sliceWidth))); + + *bitIndex = bI + sliceWidth; + fieldWidth -= sliceWidth; + } while ( fieldWidth != 0 ); +} + +/** Unpack a field from a bit string, converting from Gray code to binary. + * + */ +int +unpack( + const unsigned char * bitArray, /* The input bit string. */ + unsigned int * bitIndex, /* Index into the string in BITS, not bytes.*/ + unsigned int fieldWidth/* Width of the field in BITS, not bytes. */ + ) +{ + unsigned int field = 0; + unsigned int t; + + do { + unsigned int bI = *bitIndex; + unsigned int bitsLeft = WordSize - (bI & IndexMask); + unsigned int sliceWidth = + bitsLeft < fieldWidth ? bitsLeft : fieldWidth; + + field |= (((bitArray[bI >> ShiftRight] >> (bitsLeft - sliceWidth)) & ((1 << sliceWidth) - 1)) << (fieldWidth - sliceWidth)); + + *bitIndex = bI + sliceWidth; + fieldWidth -= sliceWidth; + } while ( fieldWidth != 0 ); + + /* Convert from Gray code to binary. Works for maximum 8-bit fields. */ + t = field ^ (field >> 8); + t ^= (t >> 4); + t ^= (t >> 2); + t ^= (t >> 1); + return t; +} |